Container and method for making container for oxygen-sensitive products

ABSTRACT

A packaging system or container for packaging one or more oxygen-sensitive products. The container includes a wall that defines an interior for receiving one or more oxygen-sensitive products. The space between the product or products and the wall defines a headspace. The headspace is filled with an inert gas and a scavenger gas. The wall has at least an inner layer and one or more outer layers. At least one of the outer layers includes an oxidation catalyst such that as oxygen diffuses from outside the container to the interior and scavenger gas diffuses from the interior to outside the container, the diffusing scavenger gas and oxygen react together with the oxidation catalyst in one or more of the outer layers substantially consuming the oxygen.

BACKGROUND OF THE INVENTION

1.) Field of the Invention

The present invention generally relates to active oxygen scavengers forpackaging.

2.) Description of Related Art

It is well known that limiting exposure of oxygen-sensitive products tooxygen maintains and enhances the quality and “shelf-life” of theproduct. By limiting the oxygen exposure of oxygen-sensitive products ina container or package, the quality of the products is maintained andspoilage or damage due to oxidation is avoided. In addition, suchpackaging also keeps the product fresh in inventory longer, therebyreducing costs incurred in disposing of expired products and restockingwith fresh products.

Some containers function as a passive barrier to oxygen, i.e. physicallyisolating the food in the container from the oxygen in the air outsidethe container. The effectiveness of relying on the container as apassive barrier is limited. Most containers are not air tight; oxygencan diffuse through the container walls over time. Additionally, foroxygen-sensitive solid foods like nuts, the voids and empty space withinthe container between the nuts and between the nuts and the containerwall may contain a significant amount of oxygen that was trapped duringpackaging.

In order to increase the oxygen barrier effectiveness of the containers,an increasing number of containers are using active barriers to protectoxygen-sensitive products. Active barriers, also referred to as activepackaging, entail the use of oxygen scavengers, which are materials thatcan chemically bind with oxygen in order to capture the oxygen before itcan cause damage to the oxygen-sensitive products.

Some packages employing oxygen scavengers rely on an iron-basedcatalyst. For example, some packages include one or more sachets, whichcontain an iron-based composition, placed in the interior of thepackage. The iron-based composition scavenges the oxygen through anoxidation process. However, formation of the sachets requires anadditional packaging operation. Also, many consumers are uncomfortableat finding something that appears foreign near their food. Another riskor danger is accidental consumption of a sachet when placing one in afood container. Alternatively, the iron-based compositions are sometimesembedded into the walls of the containers, but this degrades the wall'stransparency and mechanical properties. Another drawback to iron-basedcatalyst is the need for specific atmospheric conditions, specificallyhigh enough humidity, in the package in order for the scavenging tooccur at an effective rate.

Other packages contain oxygen scavengers within the wall structures ofthe package. Typically, the walls are made from a composition of resin,an oxygen scavenger, and a catalyst. Possible scavengers are unsaturatedhydrocarbon or ascorbic acid. Often the catalyst is a transition metalcatalyst in the form of a metallic salt. Oxidation or the scavenging ofoxygen usually begins with such structures as soon as the container orpackage is formed. However, manufacturers of the containers often muststore the containers for a time before the packager will actually usethe containers for packaging products. Therefore many of thesecontainers lose their effectiveness before being used. Some oxidizablepolymers have been developed which allow for controlled activation withthe use of a UV station. However, these types of containers may be proneto premature activation if not shielded properly before packaging.

It would be advantageous, therefore, to have a container or package withan active oxygen scavenger which does not require specific environmentalconditions, such as relatively high humidity, and is activated near orat the point where the products are placed within the container orpackage. Also, it would be advantageous for the presence of the activeoxygen scavenger to be essentially undetectable by consumers.

BRIEF SUMMARY OF THE INVENTION

The present invention addresses the above needs and achieves otheradvantages by providing a packaging system or container for packagingone or more oxygen-sensitive products. In general, the present inventionincludes a container having a wall. The wall defines an interior forreceiving one or more oxygen-sensitive products. The space between theproduct or products and the wall defines a headspace. The headspace isfilled with an inert gas and a scavenger gas. The wall has at least aninner layer and one or more outer layers. At least one of the outerlayers includes an oxidation catalyst such that as oxygen diffuses fromoutside the container to the interior and scavenger gas diffuses fromthe interior to outside the container, the diffusing scavenger gas andoxygen react together with the oxidation catalyst in one or more of theouter layers, substantially consuming the oxygen.

In one embodiment, the container's wall has an inner layer, a firstouter layer and a second outer layer. The first outer layer orintermediate layer is between the inner layer and the second outerlayer. This intermediate layer may be an adhesive for affixing the innerlayer and the second outer layer together. At least one of the layers ofthe wall may be an ethylene-vinyl alcohol copolymer, polyamide homo orcopolymer, polyacrylonitrile copolymer, PVC, PVDC, PEN or other polymerwith low oxygen permeability.

Preferably, the oxidation catalyst is a transition metal catalystselected from the group consisting of iron, nickel, copper, manganeseand cobalt. Furthermore, the transition metal may be in the form of atransition metal salt or organometal.

The scavenger gas comprises an unsaturated hydrocarbon gas and may alsoinclude a portion of hydrogen gas. The inert gas may be, for example,nitrogen, argon, or carbon dioxide.

In another aspect, the present invention provides a method of packagingoxygen-sensitive products. The method includes providing a containerhaving a multi-layer wall defining an interior and containing anoxidation catalyst in at least one outer layer of the wall, placing oneor more oxygen-sensitive products into the interior of the container,flushing the interior with an inert gas and a scavenger gas, and thensealing the product or products, inert gas, and scavenger gas in theinterior of the container.

The present invention has several advantages. Flushing the headspacewith the inert gas and scavenger gas replaces or removes oxygen withinthe container before sealing the container. The flushing, by providingthe scavenger gas, activates the oxidation process. Advantageously theflushing occurs near or at the point where the products are placed inthe container, which is a desirable time to activate the oxidationprocess. Also, the container provides active oxygen protection which isessentially unnoticeable to the consumers.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawing, which is not necessarily drawn toscale, and wherein:

FIG. 1 is a flow chart illustrating steps according to one embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawing, in which some but not allembodiments of the invention are shown. Indeed, this invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

The present invention provides a container or packaging system foroxygen-sensitive products. Examples of oxygen-sensitive products includebut are not limited to foods and beverages, pharmaceuticals,oxygen-sensitive medical products, and corrodible metals or productssuch as electronic devices. Foods and beverages that are especiallysusceptible to oxygen contamination includes beers, wines, fruit juices,carbonated soft drinks, fruits, nuts, vegetables, meat products, babyfoods, coffee, sauces, and dairy products.

In general, the container has a multi-layer wall. The wall defines aninterior for receiving the oxygen-sensitive product or products. Thespace or voids between the products and between the products and thewall define a headspace. The wall has an inner layer and at least oneouter layer. Each layer may be made from various materials includingpolymers and copolymers. For example, one or more of the layers mayinclude ethylene vinyl alcohol (EVOH), polyamide (PA), polyvinylidenechloride (PVDC), polyacrylonitrile (PAN), or polyethylene naphthalate(PEN), copolymers and blends. The preceding materials are advantageousfor forming oxygen barriers due to their relatively low oxygenpermeability qualities. Polymers or copolymers are the preferredmaterial layer in most application for a variety reasons including costand mechanical properties such as rigidity and transparency. However, ametallic material such as a foil may also be used as a barrier layer.Due to a metallic layer's extremely low oxygen permeability, it may bepreferred in applications requiring an ultra high oxygen barrier.

One or more of the layers may function as an adhesive for binding layerstogether. In addition, the most outer layer may function as a printlayer for displaying information. With the polymers, the wall may beproduced by lamination, coextrusion, extrusion blow molding,thermoforming, injection stretch blow molding or any other commercialprocess.

In one aspect of the invention, at least one of the outer layers of thewall contains an oxidation catalyst. Oxidation catalysts are well-knownin the art, and include transition metal catalysts which can readilyinterconvert between at least two oxidation states. The transition metalcatalyst may also be in the form of a transition metal salt ororganometal. Suitable transition metal catalysts comprise transitionmetals including manganese, iron, cobalt, nickel, copper, rhodium, andruthenium. The catalysts may have an oxidation state, including zero.The transition metal is preferably iron, nickel or copper, morepreferably manganese and most preferably cobalt. Suitable counter ionsfor the metal include chloride, acetate, stearate, palmitate,2-ethylhexanoate, neodecanoate or naphthenate. Particularly preferabletransition metal salts include cobalt (II) 2-ethylhexanoate and cobalt(II) neodecanoate. The transition metal salt may also be an ionomer, inwhich case a polymeric counter ion is employed. Such ionomers are alsowell known in the art. The oxidation catalyst may be added to the outerlayer or layers by mixing or blending the catalyst with the polymerresin or adhesive during the formation of the wall.

In one embodiment, the wall has an inner layer, a first outer layer, anda second outer layer. The first outer layer is between the inner layerand the second outer layer and comprises an adhesive and the oxidationcatalyst. The adhesive attaches the inner layer and second outer layertogether. As explained further below, the oxidation catalyst facilitatesthe consumption of oxygen diffusing through the wall. The second outerlayer is an ethylene vinyl alcohol copolymer and provides a passive orphysical barrier between the oxygen outside the container and thescavenger gas inside the headspace. In other embodiments, the wall has athird outer layer for displaying information.

In another aspect of the invention, the headspace is flushed with aninert gas and a scavenger gas before sealing the container. For examplepurposes, the inert gas may be nitrogen, argon, or carbon dioxide.Preferably the scavenger gas is hydrogen gas or hydrocarbon containingsingle unsaturation or multiple unsaturations. According to someembodiments, the scavenger gas may also include a small amount ofhydrogen gas. Again, for example purposes only, the hydrocarbonscavenger gas may be ethylene or acetylene. The ratio of inert gas toscavenger gas may vary by embodiment. Although in theory a higher amountof scavenger gas would protect the products longer, it is preferable tomaintain the amount of scavenger gas below the scavenger gas's lowerexplosion limit for safety purposes. (The lower explosion limit ofethylene is approximately 2.7% in air by volume. The lower explosionlimit of acetylene is approximately 2.2% in air by volume. In theory,these lower explosion limits in the present invention could be higherbecause the ethylene or acetylene is in the presence of an inert gasrather than air.)

Flushing the headspace with an inert gas and a scavenger gas isadvantageous. First, the inert gas and scavenger gas replace or removeany oxygen that would otherwise be trapped in the headspace when thecontainer is sealed. Second, as oxygen diffuses from outside thecontainer to the interior of the container over time, the scavenger gaswill diffuse from the interior of the container to the outside of thecontainer. In the presence of the oxidation catalyst within the wall,the scavenger gas and oxygen react, consuming the oxygen and protectingthe products in the container.

In yet another aspect, the present invention provides a method ofpackaging oxygen-sensitive products, as illustrated in FIG. 1. Themethod includes providing a container having a multi-layer wall definingan interior. The multi-layer wall includes one inner layer and at leastone outer layer. Furthermore, at least one of the outer layers includesan oxidation catalyst. One or more oxygen-sensitive products are placedinto the interior of the container. The space or voids between theproducts and the space between the products and the wall defines aheadspace. The headspace is flushed with an inert gas and a scavengergas. Next, the product or products, inert gas, and scavenger gas aresealed within the interior of the container.

One in the art would appreciate the numerous manners in which to seal acontainer. For example purposes only, the container may include an openend configured to sealably engage a lid or membrane closure, metal orplastic alike. Alternatively, in some embodiments, the open end may beclosed by bringing the wall together at the open end and forming a heatseal or bond between portions of the wall.

The present invention has several advantages. As stated, flushing theheadspace with the inert gas and scavenger gas replaces or removesoxygen within the container before sealing the container. The flushing,by providing the scavenger gas, activates the oxidation process.Advantageously the flushing occurs near or at the time when the productsare placed in the container, which is a desirable time to activate theoxidation process. Also, the container provides active oxygen protectionwhich is essentially unnoticeable to the consumers.

Many modifications and other embodiments of the invention set forthherein will come to mind to one skilled in the art to which thisinvention pertains having the benefit of the teachings presented in theforegoing descriptions and the associated drawing. Therefore, it is tobe understood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

1. A container for packaging at least one oxygen-sensitive product, thecontainer comprising: a wall having an inner layer and at least a firstouter layer, wherein the first outer layer includes an oxidationcatalyst; and an interior defined by the wall for receiving the at leastone product, the interior including an inert gas and a scavenger gas,such that as oxygen diffuses into the interior, the scavenger gasdiffuses out of the interior and reacts together with the oxidationcatalyst in the first outer layer, substantially consuming the oxygen.2. The container according to claim 1, wherein the wall furthercomprises a second outer layer, and the first outer layer is between theinner layer and the second outer layer.
 3. The container according toclaim 2, wherein the first outer layer comprises an adhesive foraffixing the inner layer and the second outer layer together.
 4. Thecontainer according to claim 1, wherein the oxidation catalyst comprisesa transition metal catalyst selected from the group consisting of iron,nickel, copper, manganese and cobalt.
 5. The container according toclaim 4, wherein the transition metal catalyst comprises a metal salt oran organometal.
 6. The container according to claim 1 wherein thescavenger gas comprises an unsaturated hydrocarbon gas.
 7. The containeraccording to claim 6 wherein the scavenger gas also includes a hydrogengas.
 8. The container according to claim 1 wherein the inert gascomprises either nitrogen or carbon dioxide.
 9. The container accordingto claim 1 wherein either the inner layer or the first outer layercomprises an ethylene-vinyl alcohol copolymer.
 10. A method of packagingoxygen-sensitive products, the method comprising: providing a containerhaving a wall that includes an inner layer and at least a first outerlayer, wherein the first outer layer includes an oxidation catalyst;placing the at least one oxygen-sensitive product into an interiordefined by the wall; flushing the interior with an inert gas and ascavenger gas; and sealing the product, inert gas, and scavenger gas inthe interior of the container.
 11. The method according to claim 10,wherein the oxidation catalyst comprises a transition metal catalystselected from the group consisting of iron, nickel, copper, manganeseand cobalt.
 12. The method according to claim 11, wherein the transitionmetal catalyst comprises a metal salt or an organometal.
 13. The methodaccording to claim 10 wherein the scavenger gas comprises an unsaturatedhydrocarbon gas.
 14. The method according to claim 13 wherein thescavenger gas also includes a hydrogen gas.
 15. The method according toclaim 10 wherein the inert gas comprises nitrogen or carbon dioxide. 16.The method according to claim 10 wherein either the inner layer or thefirst outer layer of the wall comprises an ethylene-vinyl alcoholcopolymer.